1. Technical Field
The present invention relates to a projector, and particularly to a technology of a projector that uses laser light to display an image.
2. Related Art
A technology using a laser light source as the light source of a projector has been proposed in recent years. A laser light source, as compared with a UHP lamp that has been used as the light source of a projector, has various advantages including excellent color reproducibility, quick start, and a long life. Laser light, which is coherent light, applied onto a screen or any other diffusing surface produces in some cases interference fringes called a speckle pattern having bright and dark dots randomly distributed. A speckle pattern is produced when light beams diffused by the diffusing surface randomly interfere. A speckle pattern recognized in a displayed image gives a viewer a sense of glaring flicker, disadvantageously affecting the viewed image. To avoid such a situation, when a laser light source is used, it is necessary to take measures against speckle noise. To reduce speckle noise, for example, JP-A-6-208089 proposes a technology for superimposing a plurality of speckle patterns by rotating or oscillating a diffuser element. In the technology proposed in JP-A-6-208089, speckle noise is reduced by superimposing a plurality of speckle patterns to make a specific speckle pattern less recognizable.
However, a mechanical driving unit, when necessary to rotate or oscillate the diffusion element, may lower the reliability of the apparatus and make the apparatus less quiet. Further, the diffusion element may be required to be highly durable against the motion of the mechanical driving unit, resulting in increase in cost. In the technology of the related art, it is disadvantageously difficult to reduce speckle noise without using a mechanical driving unit.